Worldwide, people with severe mental illness (SMI) have been found to be at extremely elevated risk for human immunodeficiency virus (HIV). A recent study has documented an HIV seroprevalence among SMI in Brazil five times higher than the general population and several studies have documented sexual risk- taking among SMI. Despite a well documented AIDS crisis in Brazil and the Brazilian government's commitment to HIV prevention for the whole society, Brazilian SMI are not regularly offered tested HIV prevention interventions. The goal of this study is to build on the successful findings of our NIMH funded pilot study (R01-65163-01) that adapted, refined, and piloted an HIV prevention intervention for men and women with SMI in Brazil, based on HIV prevention interventions found to be efficacious for the SMI in the US. Our pilot study established the need for and feasibility of conducting an RCT to test the efficacy of a theory-based, small-group, provider-delivered intervention that focuses on improving knowledge, motivation, and behavioral skills (1MB Model) to reduce HIV sexual risk behavior among SMI. We propose to continue to build our current community partnerships and to expand the collaboration to include the Municipality of the city of Rio de Janeiro. AH nine municipal community mental health clinics (Centers for Psycho-Social Assistance-CAPS) in Rio de Janeiro will serve as sites for the proposed study. Using sites that are representative of outpatient treatment delivery settings across Brazil, will inform future HIV prevention services. We propose to conduct an RCT to test the long-term efficacy of our Brazilian HIV Prevention Intervention for men and women with SMI (eight sessions plus three boosters six months later) assessing sex risk behavior at baseline, and 3, 6 and 12 months post-intervention;HIV knowledge, motivation and behavioral skills will also be assessed together with the impact of mental illness stigma and psychiatric symptoms on sex risk behavior. Our history of working together exemplifies compatible, equitable international research collaboration and partnership with bidirectional capacity building of community, academic and service setting members. This study will lay a foundation for future HIV prevention services implementation within the system of psychiatric care in Brazil. Further, if efficacious, our intervention-and the process of collaboration we used to develop it-will be a model that can be implemented in a variety of public health settings worldwide.